1. Field of the Invention
The present invention relates to a printing apparatus and a printing control method, and more particularly, to a printing apparatus and a printing control method for forming an image by scanning a recording head.
2. Description of the Related Art
A recording apparatus having the function of a printer, a copier, a facsimile apparatus or the like, or a recording apparatus used as an output apparatus for a composite electronic apparatus including a computer, a word processor and the like, or a work station is configured so as to record an image on a recording medium, such as paper, a plastic thin film or the like, based on image information. Such recording apparatuses can be classified into an ink-jet type, a wire-dot type, a thermal-recording type, a laser-beam type and the like, based on how the image is recorded.
In serial-type recording apparatuses that adopt serial scanning in which main scanning is performed in a direction crossing the conveying direction of a recording medium (a sub-scanning direction), recording on the entire recording medium is performed by recording an image using recording means mounted on a carriage which moves along the recording medium, by repeating the operation of performing sheet feeding by a predetermined amount (pitch conveyance) after completing recording for one line on the recording medium and then performing recording for the next line on the recording medium which has stopped after the pitch conveyance.
FIG. 13 is a diagram illustrating an example of accuracy in recorded positions when a recording head has performed recording on one line (measurement of deviations in the positions of dots recorded with an interval of {fraction (1/90)} inch).
In FIG. 13, the positions of recorded dots with reference to the position to start recording are shown, and the ordinate indicates the accumulated amount of deviation from the position where the dot is intended to be recorded. The positive side of the ordinate represents a deviation in a direction away from the home position of the recording head making the position to be recorded 0, and the negative side represents a deviation in a direction toward the home position.
Usually, recording is performed after the carriage motor has reached a constant speed. Hence, the carriage is moved by beginning driving the carriage motor from a position slightly before the position to start recording. As a result, as can be understood from FIG. 13, accuracy in recording is somewhat inferior immediately after starting the carriage motor for driving the carriage (i.e., near the position to start recording), such that the amounts of deviation in recorded positions are xc2x140 xcexcm-50 xcexcm. Thereafter, recorded positions are stabilized, such that the amounts of deviation are xc2x110 xcexcm-20 xcexcm.
Accordingly, for example, when recording stepwise ruled lines as shown in FIG. 14 on a recording medium P, the position to start recording differs in each scanning operation by the recording head, and the position to begin driving the carriage motor gradually changes at each step of the ruled lines. As a result, the position to start the movement of the carriage shifts from the starting position of the preceding scanning line.
This problem will be described with reference to FIG. 13.
In FIG. 13, a curve formed by black dots indicates changes in the amounts of deviation of recorded positions generated on a certain line when recording stepwise ruled lines, and a curve formed by broken lines indicates changes in the amounts of deviation of recorded positions generated on the next line. The curve formed by broken lines starts from a position different from the position of the curve formed by solid lines, because the next stepwise ruled line shifts to the right by the amount of a step portion.
When such stepwise ruled lines are recorded, then, as shown in FIG. 13, a deviation as much as about 70 xcexcm sometimes occurs between adjacent recorded lines.
Particularly, such deviations are pronounced at border portions of the ruled lines, such as positions a, b and c shown in FIG. 14, thereby causing degradation in the quality of the recorded image.
In recording apparatuses for forming black by superposing printing materials of a plurality of colors, i.e., Y (yellow), M (magenta) and C (cyan), such deviations will cause a color deviation, thereby greatly degrading the quality of the recorded image.
In order to solve such problems, for example, EP Patent Publication No. 0754559A has proposed a configuration in which, in order to remove deviations in recorded positions when starting recording, the position to start each scanning operation of the carriage is adjusted to an integer multiple of the distance of movement of the carriage according to the revolution of a stepping motor corresponding to one period of the exciting phase of the motor.
Since the vibration of the mechanical portion is dominant as the cause of the amount of deviation with respect to an absolute position from the position to start recording shown in FIG. 13, except for a case in which nonuniformity due to cogging, serving as nonuniformity in the revolution of the carriage motor itself, is pronounced, it is necessary to provide countermeasures for this vibration. This vibration has a unique period.
Accordingly, the following countermeasures have been provided.
(1) By mounting an encoder in the recording apparatus and detecting the absolute position of the carriage, accuracy in the position to form each dot for an accurate image is assured.
(2) Since a stepping motor is most commonly used for driving the carriage, the motor is started with a low number of revolutions, and recording is performed after the number of revolution of the motor reaches a predetermined value. When intending to stop the carriage, the revolution of the motor is decelerated from the used number of revolutions, and the motor is stopped after reducing the number of revolutions to a low value. By increasing the distance during the start of the motor, variations in the speed of the carriage at the number of revolutions used during recording are minimized, so that accuracy in the position to form each dot for an accurate image is secured.
However, in the above-described conventional approach, since additional components such as an encoder and the like are required, the cost of the apparatus increases. An increase in the conveying distance during the start of the motor results in a reduction of the effective recording length, or in an increase in the size of the apparatus in order to assure a sufficient effective recording length.
It is an object of the present invention to provide a recording apparatus and a recording control method which can perform accurate recording without increasing the production cost and the size of the apparatus.
According to one aspect, the present invention which achieves the above-described object relates to a recording apparatus including scanning means for mounting a recording head for forming an image on a recording medium and for performing reciprocating scanning in a first direction, conveyance means for conveying the recording medium in a second direction transverse to the first direction, input means for inputting recording data, first determination means for determining a position to start scanning of the recording head relative to the recording medium for each scanning operation during recording, based on the recording data input by the input means, setting means for setting a permitted or permissible region to start scanning in a next scanning operation, based on a position to start scanning in a preceding scanning operation, discrimination means for discriminating whether or not a position to start scanning for the next scanning operation is within the permitted region, second determination means for determining a position within the permitted region as a position to start scanning of the recording head by the scanning means, when it has been determined that the position to start scanning for the next scanning operation is outside of the permitted region to start scanning based on a result of discrimination by the discrimination means, and movement means for moving the recording head to the position determined by the second determination means.
According to another aspect, the present invention which achieves the above-described object relates to a recording apparatus including scanning means for mounting a recording head for forming an image on a recording medium and for performing reciprocating scanning in a first direction, conveyance means for conveying the recording medium in a second direction transverse to the first direction, input means for inputting recording data, first determination means for determining a position to start recording of the recording head on the recording medium for each scanning operation during recording, based on the recording data input by the input means, and setting means for dividing a recordable area of the recording medium into regions along the first direction, with each region having a predetermined width in the first direction and for setting a position to start scanning for each of the regions. The predetermined width equals a pitch of vibration of the scanning means. The apparatus also includes second determination means for determining a position to start scanning for each scanning operation, depending on which region the position to start recording is located, and movement means for moving the recording head to the position to start scanning determined by the second determination means for each scanning operation.
According to still another aspect, the present invention which achieves the above-described object relates to a recording control method applied to a recording apparatus mounting a recording head for forming an image on a recording medium and having a carriage for performing reciprocating scanning in a predetermined direction. The method includes an input step of inputting recording data, a first determination step of determining a position to start scanning of the recording head relative to the recording medium for each scanning operation during recording, based on the recording data input in the input step, a setting step of setting a permitted or permissible region to start scanning in a next scanning operation, based on a position to start scanning in a preceding scanning operation, a discrimination step of discriminating whether or not a position to start the next scanning operation is within the permitted region, and a second determination step of determining a position within the permitted region as a position to start scanning of the recording head, when it has been determined that the position to start scanning of the next scanning operation is outside of the permitted region, based on a result of discrimination in the discrimination step, and a movement step of moving the recording head to the position determined in the second determination step, before recording in the next scanning operation.
According to yet another aspect, the present invention which achieves the above-described object relates to a recording control method applied to a recording apparatus mounting a recording head for forming an image on a recording medium and having a carriage for performing reciprocating scanning in a predetermined direction. The method includes an input step of inputting recording data, a first determination step of determining a position to start recording of the recording head on the recording medium, based on the recording data input in the input step, and a setting step of dividing a recordable area of the recording medium into regions along the predetermined direction, with each region having a predetermined width in the predetermined direction and for setting a position to start scanning for each of the regions. The predetermined width equals a pitch of vibration of the carriage. The method also includes a second determination step of determining a position to start scanning for each scanning operation, depending on which region the position to start recording is located, and a movement step of moving the recording head to the position to start scanning determined in the second determination step for each scanning operation.
According to yet another aspect of the present invention, a recording apparatus includes a scanning unit, a conveyance unit, an input unit and a processor. The scanning unit includes a carriage for mounting a recording head for forming an image on a recording medium and a carriage motor for reciprocatingly scanning the carriage in a first direction. The conveyance unit conveys the recording medium in a second direction transverse to the first direction. The input unit inputs recording data. The processor determines a position to start scanning of the recording head relative to the recording medium for each scanning operation during recording, based on the recording data input by the input unit, and sets a permissible region to start scanning in a next scanning operation, based on a position to start scanning in a preceding scanning operation. The processor further discriminates whether or not a position to start scanning for the next scanning operation is within the permissible region, determines a position within the permissible region as a position to start scanning of the recording head by the scanning unit, when discriminated that the position to start scanning for the next scanning operation is outside of the permissible region to start scanning, and controls the scanning unit to move the recording head to the predetermined position.
According to still another aspect, a recording apparatus includes a scanning unit, a conveyance unit, an input unit and a processor. The scanning unit includes a carriage for mounting a recording head for forming an image on a recording medium and a carriage motor for reciprocatingly scanning the carriage in a first direction. The conveyance unit conveys the recording medium in a second direction transverse to the first direction. The input unit inputs recording data. The processor determines a position to start recording of the recording head on the recording medium for each scanning operation during recording, based on the recording data input by the input unit, divides a recordable area of the recording medium into regions along the first direction, with each region having a predetermined width in the first direction and sets a position to start scanning for each of the regions. The predetermined width equals a pitch of vibration of the scanning unit. The processor further determines a position to start scanning for each scanning operation, depending on which region the position to start recording is located, and controls the scanning unit to move the recording head to the determined position to start scanning for each scanning operation.
The foregoing and other objects, advantages and features of the present invention will become more apparent from the following detailed description of the preferred embodiments taken in conjunction with the accompanying drawings.